What are four Types of Carbon Steel and Their Use Case?

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Low carbon steel (LCS), also known as mild steel, is the most machinable and ductile carbon steel of all types. Low carbon steel is a type of steel with low carbon content, usually ranging from 0.05% to 0.25%, which makes it relatively soft and more easily to be deformed. However, for the same reason as well, it has lower strength compared with steel with higher carbon levels.

Below are the properties of low carbon steel:

1. Ease of machining: Low carbon steel can be easily cut, drilled, deformed with standard tooling, which facilitates fabrication and application requiring precise operation.
2. Cost-effectiveness and wide availability: Low carbon steel has simple composition (mainly iron and a minimal amount of carbon) and the mature production process makes it easier to produce and more accessible to the target customers.

 

Application Of Low carbon steel

Low carbon steel is gaining its popularity across the globe because of its superior ductility and weldability. Examples are listed as below categorized by sector:

1. Construction: beams, channels, and angles which make up the skeleton of the buildings.
2. Automotive industry: body panels such as car doors, trunk lids or frame components which support the car engine.
3. Domestic goods: appliances such as refrigerator, ovens and washing machines or some main components of furniture.

Common low carbon steel Grades table

The table below summarizes common low carbon steel grades, including their carbon content, typical applications, formats, and related notes.

Grade	Standard/Spec	Carbon Content (%)	Typical Uses
SAE 1005	ASTM A29/A29M, SAE J403	0.05–0.07	Wire products, nails, rivets, sheet metal
SAE 1006	ASTM A29/A29M, SAE J403	0.06–0.08	Deep drawing parts, wire, rods, tubing
SAE 1008	ASTM A29/A29M, SAE J403	0.08–0.10	Wire products, sheet, bolts, cold formed parts
SAE 1010	ASTM A29/A29M, SAE J403	0.08–0.13	Automotive panels, structural shapes, tubing, stamped parts
SAE 1015	ASTM A29/A29M, SAE J403	0.13–0.18	Shafts, rods, fasteners, small machine parts
ASTM A36	ASTM A36	≤0.26	Structural beams, channels, plates, bridges, buildings

Medium Carbon Steel

Medium carbon steel (MCS) has more carbon content than low carbon steel. Medium carbon steel is a type of carbon steel with carbon content ranging from roughly 0.25% to 0.60% by weight. Compared with low carbon steel, it strikes a delicate balance between both ductility and hardness.

Below are the major properties of medium carbon steel:

1. Higher strength and hardness: More carbon content allows a greater amount of iron carbide to form inside the microstructure, which makes it much stronger than low carbon steel at the expense of ductility.
2. Superior wear resistance: The increased hardness makes medium carbon steel less prone to wear and abrasion.
3. Capable of heat treatment: Medium carbon steel can be hardened and strengthened through heat treatment such as quenching and tempering.

 

Applications Of Medium Carbon Steel

Medium carbon steel has a vast array of applications where the optimal balance of strength and ductility is the key. Here are some of its applications in different industries.

1.  Automotive: Medium carbon steel is often used for high-stress components such as gears and shafts, bolts, studs and nuts.
2. Machinery and manufacturing: shafts and spindles, pins and keys.

Common Medium Carbon Steel Grades

Grade	Standard/Spec	Carbon Content (%)	Typical Uses
SAE 1040	ASTM A29/A29M, SAE J403	0.37–0.44	Shafts, axles, bolts, crankshafts, gears, forging parts
SAE 1045	ASTM A29/A29M, SAE J403	0.43–0.50	Machinery parts, axles, bolts, rods, gears, crankshafts, connecting rods
SAE 1050	ASTM A29/A29M, SAE J403	0.47–0.55	Springs, stamping, forged components, hand tools
SAE 1144	ASTM A29/A29M, SAE J403	0.40–0.48	Shafting, gears, spindles, machine parts (known for good machinability)

High Carbon Steel

High carbon steel, or HCS is a type of carbon steel with carbon content ranging from 0.60% and 1.00%, second only to the Ultra-high Carbon Steel. A great amount of carbon significantly enhances its hardness and strength yet reduces its ductility to a large degree. Therefore, high carbon steel is usually hard to work with since it is more likely to crack and necessitates high-standard operation practice.

Below are the properties of high carbon steel:

1.  High hardness and strength: it can hold a sharp edge without breaking and resists deformation and wears exceptionally well.
2.  Low ductility and poor weldability: it cannot be easily bent, stretched, or welded without specialized heat treatment.

 

Applications of high carbon steel

High carbon steel is often used to make tools or other items that must hold a sharp edge or resist abrasion. Here are some examples.

1.  Tool manufacturing：cutting tools such as knives, saw blades, lathe tools; hand tools such as hammers, wrenches and punches.
2. Spring manufacturing: coil springs and leaf springs especially in vehicle suspensions.

 

Common high carbon steel Grades

Below are the most common grades of high carbon steel, detailing their standards, carbon content, and typical applications.

Grade	Standard/Spec	Carbon Content (%)	Typical Uses
SAE 1060	ASTM A29/A29M, SAE J403	0.57–0.63	Springs, hand tools, blades, railway tracks
SAE 1070	ASTM A29/A29M, SAE J403	0.67–0.74	High-strength springs, saw blades, knives
SAE 1080	ASTM A29/A29M, SAE J403	0.77–0.84	Chisels, cutting tools, music wire, springs
SAE 1095	ASTM A29/A29M, SAE J403	0.90–1.03	Knife & razor blades, springs, files, hacksaw blades

Ultra-high Carbon Steel

Ultra-high carbon steel (UHCS) possesses the highest carbon content among all steel types, typically ranging from 1.00% to 2.00%. This places it at the upper limit of carbon solubility in iron.

Below are the properties of Ultra-high carbon steel:

1. Extreme strength and wear resistance: it is the hardest type in steel family owing to the massive amount of carbon content which differentiates it from others. Thus, it is exceptionally resistant to deformation and abrasion.
2. Extreme brittleness: it has comparatively low ductility at the expense of high strength. In this case, it will shatter in a brittle manner, similar to glass, when subjected to stress.
3. Superior plasticity: some grades of ultra-high carbon steel exhibit superplasticity at elevated temperatures, meaning that they can undergo tensile deformation without breaking. This benefits the formation of some complex shapes.

Applications Of Ultra-high Carbon Steel

The properties of UHCS make it suitable for demanding applications where other types of steel fall short. Here are some examples.

1.  Advanced cutting and tooling: such as surgical instruments, industrial knives or blades, and high-precision woodworking tools;
2.  High-wear-resistant components: Such as high-performance bearings with a longer contact fatigue life.

 

Common Ultra-high Carbon Steel Grades

Below are the most common grades of ultra-high carbon steel, detailing their standards, carbon content, and typical applications.

Grade	Standard/Spec	Carbon Content (%)	Typical Uses
SAE 1095	ASTM A29/A29M, SAE J403	0.90–1.03	Knives, files, springs, razor blades, saw blades
SAE 1100	ASTM A29/A29M, SAE J403	0.95–1.03	Cutlery, surgical blades, punches, chisels
SAE 1151	ASTM A29/A29M, SAE J403	1.13–1.25	High-strength wire, tools, special springs
SAE 1170	ASTM A29/A29M, SAE J403	1.13–1.20	Tool steel applications, wear-resistant parts
SAE W1	ASTM A686, SAE J437	0.70–1.50	Water-hardening tool steel, cutting tools, dies

FAQ

1. Is low-carbon steel easier to shape than high-carbon steel?

Yes. This is a fundamental difference between these two types which results from the amount of the carbon content they contain. With a carbon content of 0.25% or less, low-carbon steel consists of soft and ductile ferrite, enabling it to be easily deformed. In contrast, high-carbon steel exhibits the opposite characteristics.

 

2. Is 4140 a high carbon steel?

No. The standard classification for carbon steel is:

Low-carbon steel: 0.05% – 0.25%
Medium-carbon steel: 0.25% – 0.60%
High carbon steel: 0.60% – 1.00%
Ultra-high carbon steel: 1.00% – 2.00%.

Therefore, according to the classification, 4010 is technically a medium carbon steel.

 

3. What is the difference between high carbon steel and low carbon steel?

The most significant difference between high carbon steel and low carbon steel lies in their carbon content. Low-carbon steel contains 0.05% – 0.25% carbon, while high carbon steel contains 0.60%-1.00%. This fundamental difference in composition results in contrasting properties of the two types. Simply put, LSC is soft, ductile and easy to shape. By contrast, HCS is hard, strong and wear-resistant, but brittle and difficult to process without heat treatment.

Due to their distinct characteristics, they have different applications. LCS is widely used in the construction, automobile industry where formability and weldability are the key. HCS is commonly applied in the cases where hardness and wear resistance are paramount, such as cutting tools, springs, and high-strength components.